The use of magnetic disks for data storage has become widespread in the computer industry. Data can be stored on both sides of a magnetic disk in concentric circular recording tracks. To translate data to and from a spinning disk during read/write operations, at least one magnetic transducer is situated within microinches of a surface of the disk. To accommodate such positioning, the transducer is affixed to a specially designed platform. The platform is aerodynamically designed to fly on a thin cushion of ambulant air adjacent to the recording surface that is created by the spinning disk. The air cushion serves to define the clearance between the communicating faces of the transducer/platform combination, hereinafter referred to as a head, and spinning disk. In general, as head size is decreased, greater head stability with respect to the topography of the spinning disk can be achieved. Increased head stability minimizes the likelihood of destructive contact between the head and disk, thereby allowing the head to fly closer to the disk surface. As head/disk clearance is decreased, the density of data stored on the disk can be increased. The smallest commercially available head is shown in U.S. Pat. No. 4,167,765. The head shown therein is known in the art as a Whitney head, and is currently employed in the IBM 3370 and 3380 disk drive systems.
Each head in a magnetic disk storage system is supportably connected to a flexure. The flexure allows the head to pitch and roll relative to the associated disk's spinning surface, so that a substantially parallel relationship between the communicating faces of the head and disk can be maintained during read/write operations. Such a parallel relationship contributes to the realization of accurate data translation. Examples of different types of flexures are described and illustrated in U.S. Pat. Nos. 3,896,495, 4,167,765, ad 4,302,789.
Typically, the flexure is supportably connected to the free end of a predominantly flat, cantilevered suspension arm which is attached to a movable carriage adjacent to the associated disk. To radially access the plurality of concentric recording tracks on a magnetic disk, the carriage is oriented so as to move along a horizontal axis that coincides with a radial line extending from the center of the associated disk. Since the position of the carriage relative to the disk is electrically controllable, the head, which is operatively associated with the carriage, can be radially positioned to read from and write onto each of the concentric recording tracks.
The suspension arm, or a component member thereof, is spring-loaded in a conventional manner to provide vertical loading force on the head so as to urge the head towards the associated disk, and counterbalance the air bearing force associated with the aforementioned cushion of ambulant air. In this manner, the desired head/disk clearance can be maintained during read/write operations as variations in the disk surface are encountered. Maintenance of a near constant head/ disk clearance, and substantially parallel relationship between the head and disk as previously discussed, is necessary to insure accurate data translation and minimal head/disk destructive contact. It should be emphasized that the density of data stored on on a magnetic disk, and the signal-to-noise ratio established during data translation, can be increased as the head/disk clearance constant is decreased. Therefore, it is desirable to maintain as small a clearance constant as possible to maximize both the accuracy of data translation and the data storage capabilities of a computer system. The smallest head/disk clearance constant found in a commercially available disk drive system, is realized through the employment of a unique head/flexure/suspension arm combination, as illustrated and described in U.S. Pat. No. 4,167,765. That combination is known in the art as Whitney technology. The combination of a Whitney head, flexure and suspension arm is presently employed in the IBM 3370 and 3380 disk drive systems.
Two basic methods have been employed for loading a head onto an air cushion for read/write operations. In the first method, known as contact start/stop loading, the head is initially at rest directly on the face of a still magnetic disk. The face of the head that is adjacent to the disk surface is designed so that as the disk begins to spin, the head will be lifted off the disk surface by the ambulant air. When the disk reaches a predetermined speed, the desired disk/head clearance will be established for read/write operations.
There are three principal drawbacks to contact start/stop loading. First, when the disk begins to spin, the head must initially drag along the disk surface before it is lifted off. Such frictional contact tends to deteriorate the head and disk, and eventually necessitates replacement of both components and translation of the stored data onto another disk. These are costly consequences. The second drawback relates to the sticking of the head to the disk surface. This sticking may occur, for example, as a result of overlubrication of the disk or the presence of condensation between the communicating faces of the head and disk. In such situations, the head and disk do not readily separate when the disk begins to spin, and damage to the head/flexure combination may result. Third, storage disks are not readily interchangeable since both the head and suspension arm are typically in close spatial relation to the disk at all times. Replacement of a disk requires repositioning of the head and arm away from the disk. The addition of mechanisms to accomplish such repositioning tends to decrease the reliability of the system, and increase overall system costs. In light of increasing demands to increase data storage capabilities through the employment of removable magnetic disk cartridges, the third drawback to contact start/stop loading is becoming even more pronounced. It should be noted that the aforementioned IBM 3370 and 3380 disk drive systems employ contact start/stop loading.
The second method for loading a head onto an air cushion is known as dynamic loading. In this type of loading, the head, which is initially in a noncontact position relative to the disk surface, is loaded onto the air cushion while the disk is spinning. Perhaps the most common type of dynamic loading is realized through the employment of ramplike means. With this type of loading, known as ramp loading, the movable carriage is initially positioned so that the head is vertically and horizontally adjacent to the spinning disk. At least one stationary, independent member is positioned relative to the disk and suspension arm, so that as the carriage drives the arm towards the spinning disk a portion of the arm, or a component member thereof, will ride against the stationary member. The spring-loaded characteristic of the arm allows the arm to ride securely against the stationary member. Either the communicating face of the stationary member, or the riding portion of the arm, is at least partially designed with a ramp-like feature, so that as the head horizontally approaches the spinning disk it will experience vertical movement towards the air cushion. When the carriage approach is completed, the head will be properly positioned on a portion of the air cushion that is adjacent to the periphery of the disk surface. Specific techniques for ramp loading are further described and illustrated in U.S. Pat. Nos. 3,579,213, 4,280,156 and 4,302,789.
Dynamic loading is not subject to the second and third drawbacks described in connection with contact start/stop loading since the head is retracted from the disk during nonoperation of the system, and since replacement of a disk can be accomplished easily. There is, however, a potential problem with destructive disk/head contact when dynamic loading is employed. Such contact can occur during the loading of a head onto an air cushion, or upon unloading of the head from the cushion. Destructive contact during head loading usually occurs when vertical movement of a head towards an air cushion occurs to quickly, thereby allowing the kinetic energy of the head to drive the head through the air cushion and into the surface of the spinning disk. In addition, accelerated vertical head movement during loading operations can cause a head to flutter in pitch and roll and, since the flexure to which the head is connected is designed to permit such fluttering, a corner of the head may pierce the air cushion and collide with the disk surface. Such adverse head fluttering may also arise and lead to destructive contact when a head is vertically lifted from an air cushion too rapidly during unload operations. When ramp loading is employed, head fluttering may be initiated or compounded if the contact between the suspension arm and stationary member, during loading or unloading, is not centered about the gravitational center line for the head/flexure/ suspension arm combination. This problem is discussed and dealt with in U.S. Pat. No. 4,302,789.
Although the prior art disc1oses variously configured head loading devices, there is no showing of the use of a combination, as described in the present invention, which employs Whitney technology and includes a Whitney-type suspension arm and flexure, and Whitney-size head to dynamically load a head onto a disk in a magnetic disk drive system.